cpu/stm32: added APB12 bus multiplier entry for applicable cpus
cpu/stm32: added APB12 bus multiplier entry for applicable cpus

miri64/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,ant9000/RIOT,jasonatran/RIOT,ant9000/RIOT,miri64/RIOT,kYc0o/RIOT,kYc0o/RIOT,OlegHahm/RIOT,kYc0o/RIOT,OlegHahm/RIOT,kaspar030/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,miri64/RIOT,kYc0o/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,miri64/RIOT,ant9000/RIOT,kYc0o/RIOT,miri64/RIOT,OlegHahm/RIOT,kaspar030/RIOT,ant9000/RIOT,OlegHahm/RIOT,kaspar030/RIOT,jasonatran/RIOT,jasonatran/RIOT,ant9000/RIOT,RIOT-OS/RIOT,jasonatran/RIOT